The present invention relates to polyorganosiloxane compositions to be used for treating surfaces of papers, rubbers, plastics, or metals to give the surface non-sticky, water-repellent, wear-resistant, and slippery properties. The invention further relates to polyorganosiloxane compositions to be used to form primer coatings in order to enhance adhesion of other polysiloxane compositions when adhered to substrates.
Various types of polyorganosiloxane compositions have been used in treating substrate surfaces to make them non-sticky. First, there is a composition of a solution obtained by adding an SiH bond containing polyorganosiloxane and/or organo alkoxy silane to a polydiorganosiloxane having hydroxy radicals and then mixing an organic tin compound and an organic solvent. Secondly, there is an aqueous emulsion obtained by adding a Si-H bond containing polyorganosiloxane and/or organo alkoxy silane to a polydiorganosiloxane having hydroxy radicals and then adding a polyvinylalcohol or the like and emulsifying the composition with water. Thirdly, there is a composition consisting of a polyorganosiloxane having two or more vinyl radicals per molecule, a Si-H bond containing polyorganosiloxane, a platinum or platinum compound, and an organic solvent and/or a hardening inhibiter. These polyorganosiloxane compositions give substrate surfaces excellent non-sticky coatings, but have the tendency that the layer of cured silicone is easily removed from the substrate when a rubber or plastic is used for the substrate. Where the third composition is applied to a substrate of natural rubber, ordinary synthetic rubber, or soft polyvinyl chloride, the vulcanizing agent, vulcanizing accelerator, or plasticizer included in these substrates can reduce activity of the platinum or platinum compound, thereby preventing the composition from curing.
As a result of research into removing the above disadvantages and giving rubber and plastic surfaces good non-sticky, water-repellent, and wear-resistant properties, the present inventors have achieved the objects by mixing a polyorganosiloxane, having at least two monovalent hydrocarbon radicals attached to the silicon atom which radicals are replaced by a group possessing and epoxy group such as glycidoxy radical and/or epoxycyclohexyl radical and a silane and/or siloxane having a substituted or nonsubstituted amino radical attached to the silicon atom through at least one carbon atom and an alkoxy radical bonded to the silicon atom, or by a reaction of both ingredients. Although an acceptable composition was obtained in many respects sufficient slippery properties of the composition with one-time application could not be obtained.
As a result of further research, the inventors have found that a polydiorganosiloxane end-blocked with hydroxyl radicals can be added as an ingredient to the above-mentioned silane and/or siloxane with an alkoxy radical to make dealcoholization condensation with the alkoxy radical, placing the polydiorganosiloxane in a network structure, thereby providing the cured coating with slippery properties. They have also found that addition to this composition of polyorganohydrogen siloxane and a metallic fatty acid salt or metal salt of a carboxylic acid also cause a dehydrogenation condensation reaction between the hydroxyl end-blocked polyorganosiloxane and the polyorganohydrogensiloxane, thereby increasing the curing rate when cured with heat.